Testing for skin irritation

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Single Application Patch Test

These short-term tests are conducted to confirm that a product is not a skin irritant even under highly exaggerated exposure conditions. In the single application patch test, undiluted test material is moistened and applied to the upper arm using a small patch (smaller than the pad of a standard plaster). The patch stays in place for 4 hours, then the test site is observed for signs of irritation over the next 3 days. If the test material is irritating, the patch site will appear red, and may appear to be dry or rough. Typically, a minimum of 12 volunteer panelist will participate in a single test.

3-Patch Application Test (3-PAT)

Once a product or material has been shown to be non-irritating in a single application patch test, the next step isThis test is conducted to confirm that the product will not be irritating with exposures of even longer duration. The 3-Patch Application Test (3-PAT) is commonly used for this purpose. The exposure conditions of the 3-PAT are highly exaggerated over any exposure that would be encountered in real-life circumstances. Therefore, it is considered a very rigorous test of the potential to cause irritation.

In the 3-PAT, a dilution of the test material is applied to the upper arm using a small patch, and left in place for 24 hours and removed. After a 24 hour recovery period, it is replaced by a fresh patch. This is repeated for a total of 3 applications (i.e., three 24 hour applications in a five day period). The test site is observed for signs of irritation throughout the test, and 24 hours after removal of the final patch. If the test material is irritating, the patch site will appear red, and may appear to be dry or rough. Typically, 12 volunteer panelists are used in the 3-PAT.

Result: We tested 8 liquid products in the 3-PAT. All products caused very slight irritation reactions, which is consistent with our historical data for products that are considered to be very mild to skin. We also conducted the test using fabric swatches that had been laundered in a liquid detergent to confirm that detergent residue onon the laundered fabrics areis non-irritating. The laundered fabric swatches did not cause irritation in the 3-PAT.

21-Day Cumulative Irritation Test

This test was developed as a means of evaluating any irritant effects that may be cumulative with repeated exposure. In this test, small swatches of fabrics are laundered in detergent formulations. These are applied to the upper arms panelists five times a week for three weeks. Each application stays in place for 24 hours. The sites are observed for signs of irritation throughout the test. If the test material is irritating, the patch site will appear red, and may appear to be dry or rough.

Result: Fabric laundered in a liquid detergent was tested using 33 volunteer panelists. The fabric was only slightly irritating. This slight irritation is attributed to constant occlusion of the skin for a prolonged period of time and ; a result that is consistent with our historical data for products that are considered to be very mild to skin.

Wrist Band Wear Test

This test simulates wearing a tight-fitting garment. (Bannan, et al, 1992) In this test, swatches of knitted cotton are laundered in the detergent and placed around the wrists of volunteer panelists using a tight fitting athletic wrist band. These are kept in place for 6 hours per day on 4 consecutive days. The skin is evaluated for signs of irritation 24 hours after each application of the test material. Normally, 15 volunteer panelist are used for this type of study.

Hand Immersion Test

This test involves prolonged, repeated soaking of the hands in detergent solution to simulate and/or exaggerate the type of exposure that occurs when a detergent is used for hand laundry. (Suskind, et al, 1963) This test can involve 12-64 volunteer panelists, depending on the number of products being tested. One hand is immersed in a solution of the test product, while the other is immersed in a solution of a product for which the mildness and skin safety profile are very well known. Products can be tested at the expected hand laundry use concentration (0.1-0.5%), or at concentrations 5-10 times higher than expected use. Hands are immersed in solutions 30 minutes per day for 4 consecutive days. The condition of the hands and nails are evaluated each day.

Result: We evaluated 6 liquid product solutions (at 0.75%) and 2 powder products (at 0.5%). There were no signs of irritation.

References:

Bannan, E. A., J. F. Griffith, T. L. Nusair, L. J. Sauers. 1992. Skin testing of laundered fabrics in the dermal safety assessment of enzyme-containing detergents, Journal of Toxicology - Cutaneous and Ocular Toxicology, 11:327-339.
Suskind, R. R., M. M. Meister, S. R. Scheen, D. J. A. Rebello. 1963. Cutaneous effects of household synthetic detergents and soaps, Archives of Dermatology, 88:117-124.